Cochlear Implantation In Both Ears May Improve Speech Perception

A new study suggests that sequential bilateral cochlear implantation, or the placement of cochlear implants in both of a child’s ears through separate surgeries, has the potential to improve speech perception abilities in quiet and in noise. Cochlear implants are electronic devices that have the potential to restore partial hearing to the deaf.

Background: Binaural or two ear hearing enables optimal performance of the human auditory system. In normal hearing subjects binaural hearing is directly associated with improved speech understanding in quiet and in noise, as well as improved sound localization ability, when compared to listening with a single ear. Unilateral (hearing in one ear) and/or bilateral hearing loss may deprive individuals of these binaural mechanisms. Because of its widely recognized advantages, hearing professionals have for many years endeavored to provide effective binaural hearing to individuals with hearing impairment whenever technology has allowed.

Candidates for cochlear implantation must present with a bilateral severe-to-profound sensorineural hearing loss; however, despite loss of hearing in both ears, they receive only one cochlear implant. Until recent years, little attention was given to the deficits unilateral cochlear implant recipients might still experience by nature of being monaural listeners. In the past decade there have been numerous studies demonstrating that the majority of adult patients who receive bilateral cochlear implants are able to realize significant benefits on measures of speech perception and sound localization. Initial reports also suggest that benefits from bilateral implants may be realized by deafened children without language skills. These reports have led to increasing interest in bilateral implantation on the part of patients, parents, and hearing professionals.

A new study sets out to determine the extent to which bilateral implantation offers benefits on a number of measures. The study is particularly focused on measuring the effects of age at implantation and experience after activation of the second implant on speech perception performance. The authors of the study “Importance of Age and Post-Implantation Experience on Speech Performance in Children with Sequential Bilateral Cochlear Implants” are Brian R Peters, MD, and Jennifer Lake, both from the Dallas Otolaryngology Cochlear Implant Program, Ruth Litovsky, PhD from the University of Wisconsin - Madison, and Aaron Parkinson, PhD of Cochlear Americas. Their findings are being presented at the Annual Meeting of the American Otological Society, being held May 20-21, 2006, at the Hyatt-Regency Hotel, Chicago, IL.

Methodology: Thirty children, ages three to 13 years, were recipients of two cochlear implants, received in sequential surgeries, a minimum of six months apart. Age appropriate speech perception testing in quiet and in noise was performed preoperatively and again postactivation at three, six, and 12 months in both the unilateral and bilateral conditions in a repeated measures study design. Some older subjects were also tested at 24 months. Two-Way Repeated Measures Analysis of Variance (ANOVA) was used to determine statistical significance among device configurations and performance over time.

Results: Results for speech perception in quiet show that children implanted sequentially acquire open-set speech perception in the second ear relatively quickly (within six months). However, children under the age of eight years do so more rapidly and to an ultimately higher level of speech understanding ability than older children, consistent with the notion of a more “plastic” auditory system. Speech intelligibility for spondees in noise was significantly better under bilateral conditions than with either ear alone, and the bilateral benefit increased with time after activation of the second implant.

American Otological Society

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